In microscope apparatus with optical magnification systems, the magnification value of the magnification system can usually be freely smoothly adjusted. For many kinds of evaluations of images recorded at a particular magnification value, it is essential to know this magnification value. For example, the actual size of the object can be determined from the image of an object by means of the magnification value currently selected.
Coded microscope apparatus comprise means that electronically determine the magnification value currently selected. This can be done, for example, with an electric sensor. The microscope apparatus can also be fitted with an electric motor that adjusts the magnification. The magnification value currently selected can be indicated directly by the motor.
Many simpler microscope apparatus are not coded, however, and have no means for determining the magnification value currently selected. The magnification value therefore has to be determined manually by the user himself. For example, the user can read the value off a printed scale of magnifications.
It is also possible, as described in DE 10 2009 054 703 A1, to determine the magnification value by moving the microscope stage on which the specimen is located by a known predefined distance and evaluating the associated shifts in the images.
US 2005/0220362 describes a calibration in which a diffraction lattice is used, wherein the lattice constant or the spacings of the individual columns in the lattice are known. A magnified image of the lattice is obtained using a microscope and the spacings of the columns in this lattice are determined. The magnification value is determined using the ratio of the lattice constant to these gaps determined in the image of the lattice.
These methods of manually determining the magnification value are very complicated, laborious and time-consuming for a user. In addition, these methods all have a capacity for human error. The possibility of misreading a marking or making an error in the evaluation cannot be ruled out.
The evaluations of the images with the magnification values found also have an extremely limited reproducibility, as it is very difficult to reset the corresponding magnification value exactly with the necessary precision and accuracy at a later time.
If for example the images are evaluated automatically using software, the user generally first has to input the magnification value determined into the software. This is another possible source of human error. For example, if a series of images are taken with different magnification values, the user may input an incorrect magnification value into the software for one of the images or may forget to enter a magnification value. In this case he might, in some cases, have to repeat the entire series of images.
If an additional device is needed for manually determining the magnification value, for example a microscope stage as mentioned previously, the movement of which has to be precisely known, or a diffraction lattice with a precisely known lattice constant, this has substantial cost implications.
It is therefore desirable to provide an opportunity, for microscope apparatus with optical magnification systems, of determining the magnification value currently selected for the optical magnification system in a simple, precise and reproducible manner.